This invention relates generally to gas turbine engines, and more specifically to methods and apparatus for exhausting gases from gas turbine engines.
Gas turbine engines are used as a power source within a variety of applications. To protect the engine from the environment, and to shield a surrounding structure from the gas turbine engine, the gas turbine engine may be mounted within a module that includes an inlet area, an exhaust area, and an engine area that extends between the inlet area and the exhaust area. For example, when the gas turbine engine is used as a power source for a ship including a superstructure, the engine may be located within the hull near the waterline in a position that is outboard of the superstructure, but inboard of the superstructure external sidewall. Such an engine location facilitates reducing noise and heat generated during engine operation, while providing a secure mounting platform.
Because engines require continuous airflow for operation, within at least some known modules, the module inlet and exhaust areas include ducts to route ambient air from outside the hull to the engine, and to channel exhaust gases produced during operation of the engine from the hull, respectively. To reduce a risk of water inadvertently entering or blocking an entrance or exhaust to the module inlet ducts, the module inlet ducts and exhaust ducts are routed to emerge from the hull at elevations that are considerably higher than elevations where water typically contacts the hull. More specifically, the exhaust ducts are generally routed such that the exhaust gases are discharged upwardly adjacent the superstructure.
However, the exhaust duct area of gas turbine engines is a source of high infrared energy which may be used for targeting/tracking purposes by heat seeking missiles and/or various forms of infrared imaging systems. To facilitate reducing an infrared signature of a gas turbine engine, at least some known ships use exhaust as systems which cool exhaust gases by injecting sea water into the exhaust gas stream. Other known ships use suppressors which permit cooling air to mix with the exhaust gas stream through concentric rings surrounding the exhaust duct. In at least some other known ships, the exhaust gases are routed through a series of exhaust baffles prior to being discharged to the atmosphere. Generally, any benefits gained by such systems may be offset by losses created in acquiring the reduced infrared signature. More specifically, when the exhaust gases are cooled by cooling air, the air is generally provided at a substantial engine power loss or weight penalty. Furthermore, in other known systems, the benefits gained by such systems may be offset by comparatively large installation space requirements, complex ducting, and/or substantial weight penalties.
In an exemplary embodiment, a method for operating a gas turbine engine positioned within a module is provided. The engine includes an inlet and an exhaust, and the module includes an inlet area, an exhaust area, and an engine area extending therebetween and housing the engine. The exhaust area includes an exhaust duct and an outlet. The method comprises operating the engine such that inlet air is routed through the module inlet and into the engine inlet, discharging exhaust gases from the engine through the module exhaust duct such that the exhaust gases are routed substantially perpendicularly from the gas turbine engine, discharging exhaust gases from the module outlet such that the exhaust gases are discharged in a direction that is at least ninety degrees offset from exhaust gases flowing with in the exhaust duct, and supplying cooling fluid to the module engine area through a cooling system inlet. The method also comprises discharging cooling fluid from the module engine are a through a cooling system exhaust, such that the cooling fluid discharged from the engine area flows through the cooling system exhaust and around the module exhaust area disposed within the cooling system exhaust.
In another aspect, a gas turbine engine assembly is provided. The assembly comprises a module, a gas turbine engine, and a cooling system. The module comprises an inlet area, an engine area, and an exhaust area, wherein the engine area extends between the inlet and exhaust areas to define a cavity. The module exhaust area comprises an exhaust duct and an outlet extending in flow communication from the exhaust duct. The gas turbine engine is within the module cavity, and comprises an inlet and an exhaust. The turbine engine exhaust is adjacent the module exhaust area, and the module exhaust duct is used for routing exhaust gases discharged from the gas turbine engine exhaust substantially perpendicularly from the gas turbine engine. The exhaust area outlet is for routing exhaust gases discharged from the exhaust duct in direction that is at least ninety degrees offset with respect to exhaust gases flowing within the exhaust duct. The cooling system comprises an inlet and an exhaust. The inlet is for supplying cooling fluid into the module engine area external to the gas turbine engine. The cooling system exhaust is for discharging cooling fluid from the module engine area. The module exhaust area is concentrically disposed within the cooling system exhaust.
In a further aspect of the invention, an exhaust system for a gas turbine engine having an inlet and an exhaust is provided. The exhaust system comprises a module and a cooling system. The module comprises an inlet area, an exhaust area, and an engine area that extends therebetween. The engine is disposed within the module engine area such that the engine exhaust is in flow communication with the module exhaust area. The module exhaust area comprises an exhaust duct and an outlet, wherein the exhaust duct is for routing exhaust gases discharged from the engine exhaust substantially perpendicularly from the gas turbine engine, and the exhaust area outlet is for routing exhaust gases discharged from the exhaust duct in a direction that is at least ninety degrees offset from exhaust gases flowing through said exhaust duct. The cooling system comprises an inlet and an exhaust. The inlet is coupled to the module engine area for routing cooling fluid into the module engine area. The cooling system exhaust is coupled to the module engine area for routing cooling fluid from the module engine area. The module exhaust area is concentrically aligned within the cooling system exhaust.